Failure Analysis at Steam Condenser Fin Fan Cooler Tubes, Ras Tanura Refinery

A complete Process, Corrosion and Mechanical Engineering assessment was performed at a critical fin fan cooler condenser API 661 design located in Utilities Facilities of Ras Tanura Refinery, owned and operated by Saudi Aramco, the largest oil producer company of the world. The thorough analysis included a thermal engineering by computerized software, to determine heat exchanger efficiency and critical process parameters, a metallurgy microstructure analysis was performed in order to identify the root cause of tube recurrent rupture. The specimen extracted from the crack boundary was analyzed by chemical composition analysis, optical metallography and scanning electron microscopy analysis. The results demonstrate that subject tube cracking initiated on the internal surface, 60 psig steam/condensate side, and is a result of environmental stress corrosion cracking (SCC) induced by ammonia traces. Based on engineering analysis and a cost-effective-benefits study a decision was taken to change the tubes material from original Admiralty Brass to carbon steel SA-179, while the heat transfer area was modified by increasing the fins per unit length from 10fins/inch to 11fins/inch for both objectives, allow eliminating this recurrent failure and improving the air cooled heat exchanger duty by 1.5%.